7.1

31.

shadenorm(mu = 62, sig = 18, below = 44, col = "blue", dens = 200)

Interpretation 1. 15.87% of cell phone call plans in the United States cost less than $44 per month.

Interpretation 2. The probability that a randomly selected monthly cell phone call plan is worth less than $44 is 0.1587.

32.

shadenorm(mu = 14, sig = 2.5, above = 17, col = "blue", dens = 200)

Interpretation 1. 11.51% of refrigerators last for more than 17 years.

Interpretation 2. The probability that a randomly selected refrigerator lasts for more than 17 years is 0.1151.

33.

shadenorm(mu = 3400, sig = 505, above = 4410, col = "blue", dens=200)

Interpretation 1. 2.28% of all full-term babies have a birth weight greater than 4410 grams.

Interpretation 2.The probability of a randomly selected full-term baby with a birth weight more than 4410 grams is 0.0228.

34.

shadenorm(mu = 55.9, sig = 5.7, below = 46.5, col = "blue", dens=200)

Interpretation 1. 4.96% of all 10 year old males have heights less than 46.5 inches.

Interpretation 2. The probability of all 10 year old males with heights less than 46.5 inches is 0.0496.

35.

Interpretation 1. The proportion of all human pregnancies that have length periods longer than 280 days is 0.1908.

Interpretation 2. The probability of all human pregnancies that have length periods longer than 280 days is 0.1908.

Interpretation 1.The proportion of all human pregnancies that have length periods between 230 and 260 days is 0.3416.

Interpretation 2. The probability of all human pregnancies that have length periods between 230 and 260 days is 0.3416.

36.

Interpretation 1. The proportion of all gas tank fill ups that had a mileage greater than 26 miles is 0.3309.

Interpretation 2. The probability of all gas tank fill ups that had a mileage greater than 26 miles is 0.3309.

Interpretation 1. The proportion of all gas tank fill ups that had a mileage between 18 and 21 miles is 0.1107.

Interpretation 2. The probability of all gas tank fill ups that had a mileage between 18 and 21 is 0.1107.

7.2

5.

  1. 0.0071
  2. 0.3336
  3. 0.9115
  4. 0.9998

7.

  1. 0.9987
  2. 0.9441
  3. 0.0375
  4. 0.0009

9.

  1. 0.9586
  2. 0.2088
  3. 0.8479

11.

  1. 0.0456
  2. 0.0646
  3. 0.5203

13. -1.28

15. 0.67

17. -2.575, 2.575

33. 40.62

35. 56.16

37.

  1. 0.1587
  2. 0.1587
  3. 0.4772
  4. Yes; 0.0013; This means about 1 egg will hatch out of every 1000 eggs within less than 18 days.

39.

  1. 0.8658
  2. 0.0132
  3. 0.7019
  4. 0.1230
  5. A bag with 1475 chocolate chips is at the 96th percentile.
  6. A bag with 1050 chocolate chips is at the 4th percentile.

41.

  1. 0.4013 of pregnancies last for more than 270 days.
  2. 0.1587 of pregnancies last for less than 250 days.
  3. 0.7590 of pregnancies last between 240 and 280 days.
  4. 0.1894
  5. 0.0951
  6. Yes; 0.0043 of births are preterm, which means that about 4 out of every 1000 births are very preterm.

43.

  1. 0.0764 of rods have a length less than 24.9 cm.
  2. 0.0324 of rods will be discarded.
  3. 162 rods of the 5000 manufactured will be expected to be discarded.
  4. 11,804 rods should be manufactured by the plant manager.

45.

  1. 0.3228
  2. 0.4286
  3. This statement means that a favored team has an equal chance of winning or losing relative to the spread. Yes. A mean of 0 means that the spreads are accurate.

47.

  1. 20 days
  2. 19-23 days

56. The person did better on the SAT. Under the normal model, we find the z-score for the SAT, which equals 1.02, and for the ACT, which equals 0.96. Since 1.02 is higher, the person did better on the SAT.